(a) Field of the Invention
The present invention relates to a set of iron golf club heads.
(b) Description of Prior Art
A set of iron golf club heads is, for instance, a set of a plurality of golf club heads from 1st iron (so-called long iron) to 9th iron (so-called short iron) including pitching and sand wedges. Each structural factor of such iron golf club head depends on each setting. First, the larger the number of a golf club head is, the shorter a shaft and the larger a loft angle becomes, said loft angle being defined as an angle of a face relative to a vertical surface. Secondly, the larger the number thereof is, the larger a lie angle becomes as well, said lie angle being definied as an angle of a shaft relative to a horizontal plane. Further, as a result of the above settings, the larger the number is, the lower the center of gravity of each golf club head becomes in general.
According to the prior set of iron golf club heads, however, each position of the center of gravity relative to each face and neck is generally invariable crosswise. FIG. 4 illustrates one representative of prior iron golf club heads, in which 1 designates a head body having a face 2 at its front surface, while 3 designates a back, 4 a heel at one of the both sides of the head body 1, 5 a toe at the other thereof, the heel 4 being provided with a neck 7 extending therefrom for connecting a shaft 6 thereto. Further, MO designates a middle point of the face 2 with respect to its transversal length, which is to be target for hitting balls, while GO designates the center of gravity of the head body 1. The middle point MO and the center of gravity GO are approximately on the same normal line of the face 2 regardless of the number of the iron golf club head. However, such prior set of iron golf club heads is apt to cause the hooking of balls for short irons, while the slicing of balls for long irons.
Whereas, Japanese Patent Laid-Open No.1-113082 discloses another prior art such that the larger the number of an iron golf club head becomes, the less so-called displacement becomes to equalize the moment of inertia around each shaft regardless of the number of an iron golf club head, said displacement being defined as a distance measured crosswise between the intersection of the central axis of a shaft with a horizontal ground plane of a head body and the center of gravity thereof. With such structures, however, both tendencies to hook balls for short irons and to slice balls for long irons will rather increase.